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Introduction

During the last article in this series on the use of PowerShell with GitLab, we noticed some displays on the build console, and some results from our build that was a bit unusual.

Today, I’m going to look a bit further into how the build engine works, which will also explain some of these results we are seeing.

How GitLab CI Runner Works

It would be logical to think that the PowerShell code is run in the same location or a subdirectory of the folder where the service file is, similar to Jenkins, but after a bit of investigation, I found out this is not the case.

To look further into what was happening, let’s add a line to the script section of the YAML file, and put a Start-Sleep command in.Make it ten minutes, to give enough time to remote onto the GitLab CI Runner, and do a search for our .ps1 file stored in a subdirectory of the repository.

Use the content below for our build file.

YAML

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ps_helloworld:

script:

-functionHappyHelloWorld{

-$x="Hello world"

-Write-Output"I would just like to say $x"

}

-HappyHelloWorld|Out-File'c:\windows\temp\helloworld.txt'

-Start-Sleep-Seconds600

tags:

-windows

Save the changes

Add the updated file

Commit the changes

Push the changes

Navigate to the build section

Click on the commit

The job is running, and because of the Start-Sleep command, will continue to do so for the next ten minutes.

Discoveries

Remote onto your build server (if it is not already the same system you are accessing GitLab from.

Go to the C:\Windows\Temp

There will be a folder name of the format Build_xxxx

Double click on the folder

Within this folder is a script.ps1 file.

Open the file

The PowerShell code contained within the script: section of the YAML file is adjusted to make it suitable for returning the output we can see on the console window within a Gitlab job.

Looking at the code now, we can see that it has been changed significantly :

ErrorActionPreference has been set to ‘Stop‘.

Commands are in place to check to see if an error has occured, and if so to exit the script. This will also result in the job being flagged as having failed.

Probably the most interesting of the changes is the frequent use of Echo command which mimics the command that follows it.

This explains several things to us :

How the console output is seen on the job screen

Some lines output appeared strange because variables were undefined at the stage when the Echo command ran

Because PowerShell returns all output from a function, it explains why were receive an array when the HappyHelloWorld function is called. It consists of the intented output, but also the Echo commands.

The use of a function in our build code now becomes a challenge or possibly could be perceived as something to be avoided, since we cannot guarantee the element in the array that will contain our desired output. One way i’ve been able to get round this is to make the function return a PScustomobject, and make use of the -is operator outside of the function to obtain the value.

However, I’ve found a better approach is to minimize the actual PowerShell commands that you use in the script, and instead create a Build folder within your repository which contains files with the actual commands that you wish to use for the build. These can be dotsourced to make them available from within the script, without the need for adding custom code to handle this.

There are many other aspects and configuration settings possible within GitLab, which lets you have powerful control over your build steps. Examples of this are defining the order of execution, ignoring errors, and setting the steps to be taken after each one.

It’s also worthwhile noting that these articles do not include the use of testing, which should be part of your chain of operations. If you are not already familiar with the use of Pester, I’d recommend taking a look at the documentation and examples on GitLab. Amongst others, Jakub Jareš has also written an excellent series of articles on its use, which you can find on PowerShellMagazine.com

That’s it for this series of articles on the use of PowerShell and GitLab. Thanks for reading, and feel free to provide feedback.

Part 3 of this series on using PowerShell and GitLab CI gave us an initial insight into how to setup and run PowerShell code as part of a build script. During it, we were introduced to the YAML build file, .gitlab-ci.yml.

This article, and the following one will cover some of the gotchas I’ve encountered whilst getting to grips with this file, and how to get these working as you’d expect. Hopefully these will help save you some time setting these up.It will also touch on some oddities you might experience creating build scripts.

Overview

At this point, I’m going to continue to use the same project with the same job name, even though it will deviate from the original script we created earlier. This is to allow us to go through the situations I’ll mention slightly faster, and I’ll indicate for each example what the subject is about. Let’s begin!

Succeeds

Don’t use the TAB character

Unless you are using an editor which automatically translate the use of the TAB key into spaces, your scripts will fail. Use normal spaces.

Fails

The script below, whilst appearing indentical to the one that succeeds, uses table characters for indentation.

YAML

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ps_helloworld:

script:

-.\HelloWorld.ps1|Out-File'c:\windows\temp\helloworld.txt'

tags:

-windows

Succeeds

YAML

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ps_helloworld:

script:

-.\HelloWorld.ps1|Out-File'c:\windows\temp\helloworld.txt'

tags:

-windows

Watch Out For ScriptBlocks

The formatting for the use of a scriptblock can sometimes be a bit confusing. The final brace that closes the scriptblock should not have a ‘-‘ prefixing it. Additionally, if there is only one line of code within the scriptblock, it is not neccessary to use this prefix (but see below)

Fails

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ps_helloworld:

script:

-For($i=1;$i-le5;$i++){

-.\HelloWorld.ps1|Out-File'c:\windows\temp\helloworld.txt'-Append

-}

tags:

-windows

Succeeds

YAML

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ps_helloworld:

script:

-For($i=1;$i-le5;$i++){

.\HelloWorld.ps1|Out-File'c:\windows\temp\helloworld.txt'-Append

}

tags:

-windows

And if we actually look a the build output, we will see the details.
You might be quite correctly thinking that something looks a bit unusual with the output. This will be covered shortly……..

And a look at helloworld.txt to make sure it has worked correctly.

You Must Use ‘-‘ For Any Code Within Braces If It Consists of More Than One Line

If you have any code that surrounds itself in braces, such as a scripblock, function, or reiteration action, it will execute successfully without using the ‘-‘ character if there is only one line. However, two or more lines of code will fail.

Fails

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ps_helloworld:

script:

-For($i=1;$i-le5;$i++){

.\HelloWorld.ps1|Out-File'c:\windows\temp\helloworld.txt'-Append

.\HelloWorld.ps1|Out-File'c:\windows\temp\helloworld.txt'-Append

}

tags:

-windows

Succeeds

It is probably best to start using ‘-‘ even with one single line within braces.

YAML

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ps_helloworld:

script:

-For($i=1;$i-le5;$i++){

-.\HelloWorld.ps1|Out-File'c:\windows\temp\helloworld.txt'-Append

-.\HelloWorld.ps1|Out-File'c:\windows\temp\helloworld.txt'-Append

}

tags:

-windows

The script works, but the output on the screen is even stranger!

But the results are good….

Watch for error handling

Watch your syntax if you are wanting to use a Try..Catch block
Also, code within

Fails

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ps_helloworld:

script:

-$ErrorActionPreference='Stop'

-Try{

-1/0

}

-Catch{

-Write-Output"Theres been a division by zero action"|Out-File'c:\windows\temp\helloworld.txt'

}

tags:

-windows

Succeeds

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ps_helloworld:

script:

-$ErrorActionPreference='Stop'

-Try{

-1/0

}

Catch{

-Write-Output"Theres been a division by zero action"|Out-File'c:\windows\temp\helloworld.txt'

}

tags:

-windows

So the script has successfully executed. Again, the output on the screen is a bit strange, but let’s check the helloworld.txt file out.

However, the file itself has not been created, despite the fact that we know this should raise a division by zero error, which should mean the catch scriptblock is executed.

Functions Behave Differently Than You Would Expect

This final part is the greatest challenge i’ve come across so far, and deserves a bit extra detail. It will also be covered further in the next article in this series.

Here, we’ve modified our build script by adding a function which returns a string, and then output it to the same text file we’ve been using previously. If you want, you can verify the PowerShell code in the ISE, and also that the helloworld.txt file has been successfully created.

This would be put into our build script like this :

YAML

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ps_helloworld:

script:

-functionHappyHelloWorld{

-$x="Hello world"

-Write-Output"I would just like to say $x"

}

-HappyHelloWorld|Out-File'c:\windows\temp\helloworld.txt'

tags:

-windows

And it builds successfully

So let’s take a look at helloworld.txt

This is strange!!! There is other items there that shouldn’t be. In fact, only the last line of the file should be there.

Let’s do a bit of detective work and see if we can get more information about what’s being returned. A good starting place would be to see if we are getting a multiline string or an array returned.

YAML

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ps_helloworld:

script:

-functionHappyHelloWorld{

-$x="Hello world"

-Write-Output"I would just like to say $x"

}

-$result=HappyHelloWorld

-$result.GetType()|Out-File'c:\windows\temp\helloworld.txt'

tags:

-windows

So let’s take a look at helloworld.txt

This is real strange, an array is being returned. But we know that only a string is returned from the function. In the next article, we’ll dig deeper into what’s actually happening during the build process, which will shed some light on some of the strange things we’ve been noticing. Then we’ll also take a look at Lint, and how we can use it carry out checking of our YAML files.

Setting up a Windows GitLab Runner

Part 1 of this series on PowerShell and GitLab CI saw us setup our GIT client configuration, register and configure GitLab for our sample project, and then perform an initial clone of the project just created.

Todays blog covers the setup of a Gitlab Runner.

What is a GitLab Runner?

Quite simply, a GitLab Runner is an application which processes builds. On a Windows system, a GitLab Runner operates as a dedicated service. Because it communicates with GitLab CI through an API, there is no requirement to have the Runner on the same server on which you have GitLab CI installed. Runners can be setup on various operating systems, and additionally process multiple languages.

GitLab CI can use one or more Runners. This makes it not only handy when we are working in a heterogenuous environment, but also where we wish designated severs for our development, testing, acceptance, and production arenas.

Runners can be assigned per project, which gives us further flexibility. I find this very helpful, working in an environment with multiple untrusted forests. All I need to do is register a Runner in the respective forest, and then assign it to a project for that.

Preparation

Before we download and install the Windows Runner software, we need to get an identifier from GitLab. This will be used to associate a runner with a project.

Log back into GitLab

Click {yourname} / helloworld

Click Runners on the left hand pane

Copy the registration token in section 3 of How to setup a new project specific runner into the clipboard.

Installing and Configuring the Runner

Now we’ll actually get the runner operational on our build server.

Move gitlab-ci-multi-runner-windowsd-amd64.exe to a suitable directory. Note that this will be the directory from which the service runs. As this is a demo, I am going to place it in the Temp folder of my C: drive.

Start PowerShell as an administrator

Use Set-Location to set the current directory to the location of the file mentioned above

Use the command below to launch the configuration utility

PowerShell

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.\gitlab-ci-multi-runner-windows-amd64.exe register

You’ll now be prompted for input some information

coordinator URL : https://ci.gitlab.com

token : <paste the registration token you copied to the clipboard>

description : hellowworldrunner

tags : windows

executor : shell

Coordinator URL refers to the location that the runner looks to for communication with GitLabCI, Token the unique identifier that is used to identify your runner. Tags allow you to control when a job does or doesn’t build on a runner, and the executor refers to the type of script it will process.

If you are prompted for your current password, enter this as well.

Launch services

Find the service with the name of gitlab-runner

Note is the service is registered to run in the current context of your account.

Unless you have any specific need to keep the gitlab-runner service running in this context, carry out the following:

Stop the service

Change the Log On as: setting to the account you want it to run under. (In my case, I just set it to Local System Account.)

Start the service

That’s the Runner setup, and ready to be used, but first took a look at the location where the process runs from.

You should see a file there new called config.toml. This file contains the configuration settings that the Runner uses. It’s plain text, so you can open it in Notepad. It details the number of concurrent runners, the url of the gitlab cim, the token we used earlier for registration, name of the runnier, and other configuration data.

Now return to GitLab, and the Runners section we were just on, and press F5 to refresh the screen.

The helloworld runner should now be registered for this project!

In part 3 of this series, we’ll create our first GitLab CI build file, which will run a basic PowerShell script.